Nickel-dioxygen complexes

A much smaller amount of work has been done with nickel complexes of dmt ligands since they are more difficult to crystallize. Some complexes have been assembled combining [Ni(dmf)2] with viologen-based cations for applications in electrical conductivity and dioxygen activation.10 3-1035... 

The activation of dioxygen by the nickel complex and the generation of radicals by the reaction of the Ni(II).02 complex with ethylbenzene were proposed. Examples of reactions... 

The use of six equivalents of dihydrogen peroxide leads to a clean conversion of the dithiolate complex to the disulfonate compound. Earlier studies on oxidation of nickel thiolates showed that oxidations with dioxygen stop at monosulfinates. Our observation and the characterization of the first chelating bis-sulfonato nickel complex formed from the direct oxidation of a mononuclear nickel dithiolate, may also provide new insight into the chemistry of sulfur-rich nickel-containing enzymes in the presence of oxygen. 

The first reported nickel complexes with coordinated dioxygen were prepared according to equations (63), (64)253 and (6S)2 254-256... 

As far as late-transition elements are concerned, it is worthwhile to discuss some reactions occurring at C-bonded nickel and palladium enolates. Treatment of the nickel complex 73, derived from the afkynylenone 72 and Ni(cod)2, with dry dioxygen yielded the [3.1.0]bicyclohexane derivative 75 (equation 50), with the carbene species 74 as possible intermediate. ... 

Suzuki, M. Ligand effects on dioxygen activation by copper and nickel complexes reactivity and intermediates. Acc. Chem. Res. 2007, 40, 609-617. 

One of the articles describes F-430, a nickel complex with a cyclic ligand related to porphyrins. In strict anaerobes and in anaerobes able to withstand a low level of dioxygen, e.g. sulphur bacteria, both vitamin B12, a cobalt complex, and heme, an iron complex, are present. They too are related to porphyrins. It is then of interest to compare and contrast their functions. Vitamin B12 has been described in volume 20 (Hogenkamp HPC, Sando GN (1974) Struct Bond 20 23). In this volume the value of heme to anaerobes is stressed. Putting these three articles together we begin to see that early life had a requirement for trace elements in highly specified forms. 

The tetradentate Hgand in the complex Ni [H4]L is asymmetrical, which raises therefore the question of (i) is there C=N bond formation at aU and, if so, (ii) which of the two C-N bonds is being dehydrogenated in aerated acetone The reaction of Ni [H4]L with dioxygen was monitored spectrophotometricahy and the observed spectral changes clearly proved the formation of a half-salen nickel complex. The final spectrum obtained was practically identical with that of authentic Ni [H2]L. This means that, compared to the -HN-CH(Me) bond, the -HN-CH2 hond is the favored one for oxidative dehydrogenation. 

In addition to the nickel complexes discussed above the interaction of complexes Cu° [H4](X )l1, Cu [H4](X )l2, Fe°I [H4](Me)Ll Y and Cr [H4](Me)Ll Y (Y = monodentate anion) with dioxygen in aerated acetone was also studied. It was found that these complexes are obviously not dehydrogenated, since the vis spectra were stable for long periods of time. 

The dioxygen complexes M02(CNBu-r)2 (A/ = Ni, Pd) have been isolated in the pure state.Treating the nickel complexes with excess tert-huty isocyanide at 30°C results in the formation of Ni(CNBu-r)4 and r-BuNCO(19) ... 

The t-butyl isocyanide complexes of nickel(O) are used as starting materials for the synthesis of a number of complexes with unsaturated groups n bonded to the nickel atom in reactions similar to those given by dioxygen or diazo complexes (Sections 50.2.7.2 and 50.2.6.3). 

SO2 complexes with PPI13 have been also described.262 They have been prepared using reactions (76) and (77). A complex of formula [Ni(CNBu )3(S02)] has been prepared according to reaction (78).257 It reacts with dioxygen to give the sulfato nickel(II) complexes according to reaction (79). 

The chemistry of oxo compounds of nickel(II) is very limited if the simple oxide NiO and the mixed-metal oxide Ba3Ni04 are excluded.1475-1477 Dioxygen complexes of nickel(H) are not cited in a recent review article.1478... 

In the most important series of polymers of this type, the metallotetraphenylporphyrins, a metalloporphyrin ring bears four substituted phenylene groups X, as is shown in 7.19. The metals M in the structure are typically iron, cobalt, or nickel cations, and the substituents on the phenylene groups include -NH2, -NR2, and -OH. These polymers are generally insoluble. Some have been prepared by electro-oxidative polymerizations in the form of electroactive films on electrode surfaces.79 The cobalt-metallated polymer is of particular interest since it is an electrocatalyst for the reduction of dioxygen. Films of poly(trisbipyridine)-metal complexes also have interesting electrochemical properties, in particular electrochromism and electrical conductivity.78 The closely related polymer, poly(2-vinylpyridine), also forms metal complexes, for example with copper(II) chloride.80... 

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